1. Field of the Invention
The present invention relates to disk drives. More particularly, the present invention relates to head stack assemblies and disk drives using a reversed direction head gimbal assembly.
2. Description of the Prior Art
A typical hard disk drive includes a head disk assembly (xe2x80x9cHDAxe2x80x9d) and a printed circuit board assembly (xe2x80x9cPCBAxe2x80x9d). The HDA includes at least one magnetic disk (xe2x80x9cdiskxe2x80x9d), a spindle motor for rotating the disk, and a head stack assembly (xe2x80x9cHSAxe2x80x9d); that includes a read/write head with at least one transducer for reading and writing data. The HSA is controllably positioned by a servo system in order to read or write information from or to particular tracks on the disk. The typical HSA has three primary portions: (1) an actuator assembly that moves in response to the servo control system; (2) a head gimbal assembly (xe2x80x9cHGAxe2x80x9d) that extends from the actuator assembly and biases the head toward the disk; and (3) a flex cable assembly that provides an electrical interconnect with minimal constraint on movement.
A xe2x80x9crotaryxe2x80x9d or xe2x80x9cswing-typexe2x80x9d actuator assembly comprises a body portion that rotates on a pivot bearing cartridge about a pivot axis between limited positions, a coil portion that extends from one side of the body portion to interact with one or more permanent magnets to form a voice coil motor, and an actuator arm that extends from an opposite side of the body portion to support the HGA.
A typical HGA includes a load beam, a gimbal attached to an end of the load beam, and a head attached to the gimbal. The load beam has a spring function that provides a xe2x80x9cgram loadxe2x80x9d biasing force and a hinge function that permits the head to follow the surface contour of the spinning disk. The load beam has an actuator end that connects to the actuator arm and a gimbal end that connects to the gimbal that carries the head and transmits the gram load biasing force to the head to xe2x80x9cloadxe2x80x9d the head against the disk. A rapidly spinning disk develops a laminar airflow above its surface that lifts the head away from the disk in opposition to the gram load biasing force. The head is said to be xe2x80x9cflyingxe2x80x9d over the disk when in this state.
As shown in FIG. 1, some early HGAs 100 included a number of wires 102 within a tube 104 attached to a side of the actuator arm (not shown in FIG. 1). Herein, the terms xe2x80x9cproximalxe2x80x9d and xe2x80x9cdistalxe2x80x9d refer to the relative positions of a structure with respect to the pivot axis. For example, the proximal end of a structure is closer to the pivot axis of the actuator arm than is the same structure""s distal end. Consistent with the foregoing, the proximal end of each of the wires 102 emerging from the proximal end of the tube is typically soldered to the flex cable. The distal end of each of the wires 102 emerging from the, distal end of the tube 104 may be attached to a corresponding conductive pad of the transducer 106 attached to the trailing edge 108 of the head 110 (the edge of the head 110 that trails as the disk 112 rotates, under the head 110 in the direction indicated by arrow 114). In turn, the head 110 is attached to the gimbal 116 that is supported by the load beam 118. In this configuration, the wires 102 are typically unsupported as they loop from the distal end of the tube to the conductive pads on the transducer 106.
This configuration was adequate for early HGAs. However, more recent developments in the disk drive industry, such as the continuing miniaturization of slider assemblies (including the. head and the transducer) and the transition to magnetoresisitive (MR) heads have led to abandoning such looping wire configurations in favor of a configuration wherein conductive traces are laid on a polyimide film formed on the gimbal assembly. Such technologies are variously named TSA (Trace Suspension Assembly), NSL (No Service Loop), FOS (Flex On Suspension) and the like. Whatever their differences, each of these technologies replaces the discrete twisted wires 102 shown in FIG. 1 with conductive traces (copper, for example) on a layer of insulating material (such as polyimide, for example). These conductive traces interconnect the transducer elements of the head to the drive preamp and the circuits associated therewith.
A conventional TSA-type HGA 200 is shown in FIGS. 2 and 3. As shown therein, a layer of conductive material is deposited or otherwise formed onto a layer of polyimide on the gimbal 216 and selectively etched to create the conductive traces 222 and the polyimide layer(s) 220. A weld 224 electrically connects the transducer 206 to the conductive traces 222. As in the HGA 100 depicted in FIG. 1, the transducer 206 is attached to the trailing edge 208 of the head 210. The conductive traces 222, as best seen in FIG. 2, are coupled to the trailing edge of the head 210 and are routed back in the proximal direction toward the HGA""s flex circuit and preamp (not shown in FIG. 1, see FIG. 9) via a lateral extensions of the gimbal 216 called outriggers, as shown at reference numeral 226. However, the outriggers 226 negatively impact the inertia and stroke of the HGA 200, and degrade the performance of the drive in which the HGA 200 is deployed.
In an effort to reduce the HGA""s inertia and stroke, FOS-type designs similar to that shown in FIGS. 4 and 5 have been proposed. As shown therein, the HGA 400 includes conductive traces 422 formed on a polyimide layer 420 that are routed under the head 410 and back toward the flex circuit and preamp without using outriggers on either side of the head 410. This reduces the size of the gimbal 416 and correspondingly reduces the HGA""s inertia and stroke, but disadvantageously increases the separation between the load point 426 (load point between the load beam 418 and the gimbal 416) and the center of gravity 428 of the head 410.
What are needed, therefore, are improved HGAs, HSAS. In particular, what are needed are improved disk drives, HGAs and HSAs that have reduced inertia and stroke, that do not use discrete wires or outriggers and that do not exhibit an unacceptable vertical separation between the HGA load point and the center of gravity of the head.
Accordingly, this invention may be regarded as a head stack assembly for a disk drive Shaving a disk. According to the present invention, the head stack assembly comprises a body portion including a bore defining a pivot axis; an actuator arm cantilevered from the body portion and a head gimbal assembly supported at the actuator arm. The head gimbal assembly includes a load beam, which includes a first load beam surface facing toward the disk and a second load beam surface facing away from the disk. A plurality of conductors are at least partially supported by the first load beam surface. Each conductor includes a proximal conductive pad, a distal conductive pad and a conductive path between the proximal and distal conductive pads, the proximal conductive pad being closer to the pivot axis than the distal conductive pad. A gimbal is coupled to the load beam, the gimbal including a gimbal proximal end that supports the respective distal conductive pads and a gimbal distal end. A head is attached to the gimbal, the head including a head proximal end and a head distal end. The head distal end is closer to the gimbal distal end than the gimbal proximal end and the head proximal end is disposed adjacent the respective distal conductive pads. A plurality of head conductive pads are coupled to the head proximal end. The head gimbal assembly also includes means for electrically connecting each of the plurality of head conductive pads to a corresponding distal conductive pad.
According to further embodiments, the plurality of conductors may include an array of conductive traces. The array of conductive traces may define a plane substantially parallel to the pivot axis. The connecting means may include solder or gold bond bonding, for example. The head may include a transducer mounted to the head proximal end and the plurality of head conductive pads may be electrically coupled to the transducer.
The present invention may also be viewed as a magnetic disk drive comprising a disk, the disk including a recording surface, and a head stack assembly. The head stack assembly comprises a body portion including a bore defining a pivot axis, an actuator arm cantilevered from the body portion and a head gimbal assembly supported at the actuator arm. The head gimbal assembly includes a load beam, the load beam including a first load beam surface facing toward the recording surface and a second load beam surface facing away from the recording surface. A plurality of conductors are least partially supported by the first load beam surface and each conductor includes a proximal conductive pad, a distal conductive pad and a conductive path between the proximal and distal conductive pads. The proximal conductive pad, according to the present invention, is closer to the pivot axis than the distal conductive pad. A gimbal is coupled to the load beam, the gimbal including a gimbal proximal end that supports the respective distal conductive pads and a gimbal distal end. The head gimbal assembly also includes a head for flying above the recording surface of the disk while reading magnetic data recorded on the respective surface of the disk as the disk spins in a rotational direction. The head includes a leading edge and a trailing edge, the leading edge being closer to the gimbal distal end than the gimbal proximal end and leading the trailing edge over the disk as the disk rotates in the rotational direction. A plurality of head conductive pads are coupled to the trailing edge of the head and each of the plurality of head conductive pads are electrically connected to a corresponding distal conductive pad.
The present invention is also a head gimbal assembly for a head stack assembly of a disk drive having a disk that includes a recording surface. The head stack assembly includes a body portion including a bore defining a pivot axis and an actuator arm cantilevered from the body portion. The head gimbal assembly includes a load beam, which includes a first load beam surface facing toward the recording surface and a second load beam surface facing away from the recording surface. A plurality of conductors are at least partially supported by the first load beam surface, each conductor including a proximal conductive pad, a distal conductive pad and a conductive path between the proximal and distal conductive pads. The proximal conductive pad is closer to the pivot axis than the distal conductive pad. A gimbal is coupled to the load beam, the gimbal including a gimbal proximal end that supports the respective distal conductive pads and a gimbal distal end. The head gimbal assembly further includes a head for flying above the recording surface of the disk while reading magnetic data recorded on the recording surface of the disk as the disk spins in a rotational direction. The head includes a leading edge and a trailing edge, the leading edge being closer to the gimbal distal end than the gimbal proximal end and leading the trailing edge over the disk as the disk rotates in the rotational direction. A plurality of head conductive pads are coupled to the trailing edge of the head and each of the plurality of head conductive pads are electrically connected to a corresponding distal conductive pad.
The foregoing and other features of the invention are described in detail below and set forth in the appended claims.